The city of Portland, Ore., announced this week that it had begun divesting itself of its holdings in Walmart, citing concerns over the company’s ethics and labor practices.

On Thursday, the first of Portland’s Walmart bonds matured, reducing its holdings in the country’s largest retailer by 25 percent. The move may make it the first municipality in the country to drop investments in the giant retailer.

“We as a city talk a lot about our progressive values,” said Commissioner Steve Novick. “We care about working people, we care about the environment, we care about human health — and money talks. We don’t want our money to be saying things that are at cross purposes with values we profess every day.”

In October, Portland’s City Council decided it would not buy more Walmart bonds after its existing holdings matured (state law prohibits the city from investing in stocks).

The city is devising a process to evaluate other companies in its investment portfolio.

So far, only Walmart has made the hands-off list.

“Right off the bat, we knew we were comfortable putting them on the do-not-buy list based on information that is widely, publicly available,” Mr. Novick said. He said the company’s labor, wage and union practices were a concern, as well as a bribery scandal that erupted in 2012.

When this policy was adopted, the city had five Walmart bonds totaling $36 million. which was 2.9 percent of its portfolio. As of Thursday, its bonds total $27 million.

Some municipalities have policies against investing in certain industries, like fossil fuels. Amherst, Mass., for example, has a policy against investing in fossil fuels, according to the town’s financial director, Sandy Pooler, who added that it did not have any such holdings at the time the policy was approved. Amherst has no formal policy against investing in tobacco companies, but it has declined to invest in them for several years.

Singling out a particular company appears to be much more unusual.

Randy Hargrove, a Walmart spokesman, said the company would not comment on investment decisions made by others. He said that Walmart employed 550 people in the Portland area and planned to hire 600 more at new supercenters. He said the average wage for full-time hourly employees in Oregon was $13.20 an hour. He also pointed to a report the company issued recently detailing changes made to its global compliance program.